1300 Henley Court Pullman, WA 99163 509.334.6306 www.digilentinc.com PmodGYRO Reference Manual Revised April 12, 2016 This manual applies to the PmodGYRO rev. A Overview The PmodGYRO is a 3-axis gyroscope powered by the STMicroelectronics L3G4200D. By communicating with the 2 chip through SPI or I C, users may configure the module to report angular momentum at a resolution of up to 2000 dps at an output rate up to 800Hz. Features include: 3-axis MEMS digital gyroscope with high shock survivability Get angular momentum data with user selectable resolution (250/500/2000dps) Two customizable interrupt pins User configurable signal filtering Power-down and Sleep modes Small PCB size for flexible designs 1.0 in 0.8 in (2.5 cm 2.0 cm) 12-pin Pmod port with SPI interface and additional IC interface Library and example code available in resource center The PmodGYRO. 1 Functional Description The PmodGYRO utilizes ST L3G4200D gyroscope to provide motion sensing data on each of the three Cartesian axes. Users may configure both the resolution and filtering options for the measured data. 2 Interfacing with the Pmod The PmodGYRO communicates with the host board via the SPI or IC protocols. By driving the Chip Select (CS) line to a logic low voltage state, SPI mode is enabled. The first byte sent over SPI informs the on-board chip if a read or write command is going to be issued, if the register address should be incremented after a particular command has been completed, and the 5 bit address of the register that is to be written to. An example timing diagram for SPI read and writes from the L3G4200D datasheet is provided below: Copyright Digilent, Inc. All rights reserved. DOC : 502-215 Page 1 of 3 Other product and company names mentioned may be trademarks of their respective owners. PmodGYRO Reference Manual Figure 1. Timing diagram. Correspondingly, if the CS line is left at a high voltage state by an internal pull-up resistor, the IC mode of the PmodGYRO is enabled. The on-board chip has two possible slave address in the form of 110100x where x is the voltage state of the Master-In-Slave-Out (MISO) pin on the SPI header. After the slave address and the read or write bit has been transmitted and the message was acknowledged, a 7-bit register address can then be transmitted. The most significant bit (the first bit of the 8-bit of the transfer) indicates if multiple bytes of information are to be transferred. An example transfer scheme for a master device reading multiple bytes of data from the PmodGYRO is provided below: Master Slave Start Slave address and Write bit ACK Multi-byte bit and register address ACK Restart Slave address and read bit ACK Data ACK Data ACK Data NACK Stop Table 1. Example transfer scheme. Data is recorded and stored within the registers of the L3G4200D in degrees per second (dps). Correspondingly, a measured value of 360 dps is equivalent to 60 rpm. Users can retrieve data from the PmodGYRO by following the provided code example. Copyright Digilent, Inc. All rights reserved. Page 2 of 3 Other product and company names mentioned may be trademarks of their respective owners.